Liquid crystal materials have made it possible to fabricate devices such as retarder plates and lenses whose properties can be switched by generating an electric field. Lenses with variable or switchable focal length, based on liquid crystal materials, are well-known and used in many applications. The cost, size, weight, reliability, and lifetime of many systems that employ switchable or variable lenses based on liquid crystal materials may be reduced compared to that of similar systems in which switching or variability of optical properties is produced by physically moving conventional optical elements such as lenses and mirrors by motors and gears.
It is often the case that the optical properties of systems in which light propagates through liquid crystal materials is dependent on the polarization of the light. For example, although the focal length of lenses fabricated from traditional refractive optical materials such as glass is typically the same for any polarization, the focal length of many lenses fabricated wholly or partially from liquid crystal materials typically depends on polarization.
This difference between the properties of refractive optical systems based on traditional optical materials such as glass, and the properties of refractive optical systems based on liquid crystal materials, is due to the fact that traditional refractive optical materials are optically isotropic, whereas liquid crystal materials are typically anisotropic.
In many optical systems, sensitivity of optical properties to the polarization of light is highly undesirable. Therefore, much effort has been expended to find ways of obtaining the highly desirable features of optical systems fabricated with liquid crystal materials, including the ability to switch or vary the focal length, without incurring the disadvantage of sensitivity to polarization.
One of the design methods that has been used to create switchable lens systems for which the focal length is independent of the polarization of light is to employ two switchable liquid crystal based lenses in the switchable lens system, one of which has a shorter focal length in the off (unpowered) state than in the on (powered) state for one linear polarization of light, and the other of which has a shorter focal length in the off (unpowered) state than in the on (powered) state for the other linear polarization. With two switchable liquid crystal lenses, the overall focal length of the lens system is made to be independent of polarization in both the off (unpowered) state and the on (powered) state, and the overall focal length changes between the off (unpowered) and the on (powered) state.
Although the design method employing two switchable lenses makes it possible to create lens systems with switchable focal length, and for which the focal length in independent of polarization in both the states of the lens system, the need to have two separate switchable lenses is highly undesirable in some applications. For example, in contact lens systems with switchable focal length, the thickness of the contact lens system could be smaller if only one of the lenses comprising the contact lens system needs to be switched. Since user acceptance is sensitive to the thickness of the contact lens system, it would be highly beneficial to the viability of a contact lens design if only one switchable lens were needed, instead of two.
Thus, there is a need for an energized lens system with switchable focal length, for which the focal length is independent of the polarization of light in both of the two states of the system, and in which only one lens of the energized lens system needs to be switched in order to change the focal length of the energized lens system.
Thus, the need exists for solutions to the above problems with the prior art.